Water Quality

I post this photo because I’ve been working on this stream for a while to solve a mystery. The water quality is good here – surprisingly good for an urban stream – and the insects you find here frequently back that up. I’ve found riffle beetles and stoneflies here on occasion, insects that are only found in very clean waters. However, you don’t find them every time. In fact, you usually find almost no insects at all!

For the past three years, I’ve been working with some high school students to study this stream to try to explain the lack of insects. What we’ve found so far suggests that flooding is the primary factor influencing the insect population in this stream. While we still need to collect more data, particularly after a flood event, to be sure that it’s the flow that drives the lack of biodiversity in this stream, but I’m feeling more and more confident that this is the case and that we’re close to finally solving this mystery.

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Hey everyone! Took me a bit longer to get back on track after my recent travels and some very busy time at work, but I’m getting a Friday 5 up today. Woo! Feeling good about that.

I spent a big chunk of today working with various volunteers to collect data around the field station. We tracked one of our box turtles this morning, and then I had a quick lunch before one of my school groups came out for their regular data collection. The group I was working with today is a really excellent group of high schoolers from a nearby charter school. They’re incredibly smart (they know it, but they’re really down to earth too) and they are all excited about learning. They come every three weeks after school with their biology teacher to work with me as part of a research club they’ve developed at their school. That’s right: these young men and women are coming to do science for fun on their own time, just because they want to learn something. How can you resist loving a group like that?!

We have examined the stream to try to understand why there are so few insects living in what seems to be lovely water. I’ve mentioned in a past blog post that I think flooding is to blame in this particular case, but my high schoolers are helping me monitor the stream as we try to solve the mystery of the missing bugs together. They actually did a lot of the prep work for the project and have developed their own protocols and methods for the sampling they do. I think it’s awesome, so let me take you through today’s visit so you can learn about what they’re doing! First, we measured several water quality parameters:

Measuring the water

We’re using Vernier probes for this. Someday I’d love to get a grant to buy a Hydrolab or some other swanky probe so we can measure all the water quality parameters at one time rather than plugging and unplugging every probe to get the readings, but for now it’s a long, involved process to get the data recorded. We’re looking at temperature, dissolved oxygen, flow, salinity, nitrate, conductivity, turbidity, and pH. Then we collect an insect sample from the stream. I sadly didn’t get a photo of this part of the process, but they lay down what is essentially a quadrat (a plastic frame they built themselves) in the stream, hold a net at the end, and shake the hell out of the materials inside the quadrat to wash any insects into the net. It’s a sort of MacGuyvered serber sampler. Works pretty well!

Once we have a sample in the net, we sort the insects from the rest of the crud that ends up in the net with the insects:

Picking bugs

Picking is a pretty easy process. You just dump the sample into a white dish pan and remove any bugs you find. We transfer any bugs we find into a super fancy sorting tray:

Sorting tray

Okay, okay, so our sorting trays are ice-cube trays. They work well! At this point, all the insects are still alive, swimming around in the water. Everyone watches them moving around and makes comments about what they think they might be doing. However, because we can’t identify them down to a useful level at the stream, we preserve the bugs in alcohol and the group takes their samples back to school with them. We’re planning a sorting/identification date so we can identify our insects to family and genus, and then all the data will go into a database. At some point, we’ll tackle the data analysis and see what sorts of water parameters might be leading to the lack of insects in the stream. Over the 3-4 years we’re planning to keep this project going, we’ll also be able to see seasonal patterns in the life histories of several of the insects and will document the aquatic insects living in the Prairie Ridge stream in a systematic way for the first time.

While I know the group enjoys the data collection part of the experience, we typically take the scenic route back to the top of the hill, wandering slowly about the grounds. We’ve sampled grapes and persimmons. We’ve watched birds and looked at plants. We go exploring up and down the stream. A couple of trips ago, the group found an enormous cow femur in one of the pools upstream of their sampling area, and that was absolutely thrilling to them! This time we wandered down to look at the pool where the damselfly nymphs live, and it had some lovely reflections:

Roots at the stream

And just because they hadn’t done it yet, today we wandered into the Nature PlaySpace, a nature-based play area we recently built for families with young kids to help get everyone out in nature. I’ve got to say that it was really entertaining to see high schoolers running all over the play area like maniacs, sliding down the slide, and climbing up the center of the mole hill:

Mole hill. The port with the ladder comes out of the center of the hill.

Five of them packed into the opening at the top of the mole hill at one point and had their teacher take a picture of them. They all giggled the whole time!

All in all, a pretty good day! A little chilly, but I spent a lot of time in the water, and that’s always good. Add a bunch of enthusiastic volunteers into the mix and it’s even better!

Hope everyone has a good weekend, and to my American readers, have a great LONG weekend!

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Last week, the Bug Geek issued a challenged to the science blogging community: explain your research to 10-year-olds in 250 words or less. She’s writing an application that will allow her to do science outreach with kids and part of it is writing a description of her work to 8- to 12-year-olds. She thought it was a good experience for everyone. I adore doing outreach and I work with a lot of kids, so being able to communicate to the younger crowd about science is something near and dear to my heart. So, I sat down and started typing out my response to the challenge immediately.

I promptly ran into a roadblock though: I couldn’t talk about all three areas of research I’ve been involved with in only 250 words. And it turns out that I wasn’t the only one with this problem! Ted MacRae at Beetles in the Bush ended up writing one paragraph for his actual work dealing with genetically modified crops and another for his full-time hobby of collecting and describing beetles from around the world. In the end, I decided to choose only one area of research, my work monitoring aquatic habitats using insects, and focused on that. Maybe I’ll write two more paragraphs describing my work with giant water bug egg respiration and my dragonfly swarm research in the future, but for now I present my exactly 250 word summary:

Me sampling for aquatic insects. Photo by Dave Walker.

I love bugs! In fact, I love them so much that I got a job working with them. I am an entomologist, a scientist who studies insects! But not just any entomologist. I study insects that live in the water, aquatic insects. Did you know there are thousands of species of insects that live in lakes and rivers? Some have really interesting structures like snorkels to help them breathe or suction cups to keep from being washed away in a river. They have fun names too, like caddisfly, predaceous diving beetle, and water scorpion! All of these underwater insects have a place they belong and a job that they do that ultimately help the plants and animals that live with them survive.

Studying aquatic insects is important because they can tell us about the water they live in, like whether their water has been polluted or flooded. We often drink the water that insects live in, so we can tell if water is safe and unpolluted by looking at the insects living in it. If there are a lot of insects that like clean water, then there has been little pollution or other problems in the water. If you find mostly insects that can live in very dirty water, that tells you that there is something wrong and you can try to fix the problem.

By studying aquatic insects, I am learning more about our world, but also helping the people who live here. I have the best job ever!

Me Sampling the Salt River

I work with a lot of second graders, so I think this statement might actually be a bit young for the average 10-year-old. I adjust how I speak about my work based on the average intellectual level of whatever group I’m working with. It’s a lot harder to do that in print though! So, I’m hoping I don’t insult any 4th graders out there by being condescending.

Now, how to summarize why I study giant water bug egg respiration in 250 words or less… Yikes, that’s going to be a tough one!

(Morgan Jackson at Biodiversity in Focus also took up the Bug Geek’s challenge and described his work with fly taxonomy in his 250 word statement. It’s really great, so I recommend that you head on over and check it out!)

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Aquatic insects and other invertebrates have been used as indicators of water quality for about 40 years. Insects can be found in a huge variety of freshwater habitats year round and can tell scientists and water resource managers a great deal about the conditions within a body of water. By simply scooping some insects out of a stream and identifying them (that is the hard part), you can assess the conditions of the stream’s water relatively cheaply, easily, and reliably. I suspect that their use in water quality assessments drives most current research on aquatic insects – they’re that valuable.

However, using aquatic insects as indicators of water quality only works if you’re able to identify the insects that you pull out of a body of water and know something about the sorts of habitats the species you find typically inhabit. What happens if you want to do water quality assessments in an area where aquatic insect habitats aren’t all that well-known, or a place where many species haven’t even been identified? Such areas are at a disadvantage because they are unable to rely on a valuable insect tool for determining their water quality. Unfortunately, the areas that would typically benefit most from a cheap, easy, and reliable insect-based assessment of water quality are also areas where the freshwater insects aren’t known well enough to make it work.

This is exactly the sort of situation that you find in Mexico and several South American countries. One of the big problems is that no one’s really bothered to describe the aquatic insects. If an insect lives on land, there’s at least a chance that someone somewhere has gone through the trouble of describing it, but in the water… That’s a whole different matter. What ends up happening is that certain groups of aquatic insects that are terrestrial as adults have been incompletely described and the immatures remain obscure. In many common damselfly and dragonfly species, for example, people have no idea what the nymphs look like! And, if you can’t identify the aquatic insect species in a region, you can’t use them to assess water quality, making things like odonates useless as indicators.

This is the situation that researchers Daniel de paiva Silva, Paulo De Marco, and Daniela Chaves Resende faced in Brazil. They were interested in using aquatic insects as indicators of water quality, but they are incompletely described in their area, especially the odonates. So, they wondered: since odonates lay eggs in water, females choose males based on characteristics of their territories that are conducive to the survival of their offspring, and nymphs typically grow in the same areas where adult males patrol, is it possible to use the adults as a measure of water quality instead of the nymphs? With all the habitat assessments odonates apparently do on their on as they choose where to lay their eggs, it just might work!

The team tested their idea along the Turvo Sujo River in southeastern Brazil. The river is impacted by humans along a large part of its length, especially near the urban area of Viçosa. Upstream of the city the banks of the river have been converted from the natural forest lands into pastures. Donwstream of the city the river is surrounded by pastures as well, but is influenced by the city too, especially by sewage. By comparing the odonate species and water quality at six sites upstream of the city and six downstream, the researchers hoped to determine whether it was possible to use odonate adults in place of nymphs to assess the quality of water. They assumed that the downstream sites would be more polluted and would have fewer adult dragonflies relative to upstream. If there was greater abundance and species diversity of odonates at the upstream sites, they could argue that they were useful as indicators of water quality.

Their efforts were, unfortunately, largely unsuccessful due to one major issue in their design: both the upstream and the downstream sites were so impaired by land use, pollution, and other factors that there was less of a difference between the two areas than they expected and there was no real control. They found that because the forest had been replaced by pasture, many perching species of odonates that would normally be found in the area were conspicuously absent both up and downstream. The team measured several water quality parameters in the two areas and found that they were nearly identical apart from a slightly lower dissolved oxygen level downstream of the city. The diversity of odonates was a little higher at the upstream region, but only in the wet season, and a few species of damselflies dominated both areas in abundance. All in all, the upstream and downstream areas were very similar.

So, the researchers didn’t get the answers they sought and were unable to determine whether adults odonates could be used instead of nymphs in water quality studies. Instead, they learned that when humans, with their sophisticated water measuring tools, can barely tell the difference between the water quality of two areas, the odonates can’t seem to tell the difference either. They also learned that because the riparian vegetation along the river had been destroyed, the rest of the water quality parameters no longer seemed to matter. And, they found that most of the odonates along the river were exactly the sorts of species you expected to find in rivers that are highly impacted by humans. The river had been so completely altered that several pond species were even found mixed in with the river species, a clear sign of river impairment at both ends of the city.

Even though this particular study didn’t support using adult odonates in place of nymphs for water quality analyses, I think the authors have a really great idea that should be pursued by other researchers. Their argument is sound: odonates are assessing water quality to ensure the survival of their offspring, so using adult odonates in place of immatures to make those cheap, easy, and reliable studies of water qualities might be possible. And if it turns out that it works, well that would be an amazing thing! Adult odonates are big, beautiful, showy insects that people pay attention to. The adults are well described in many areas where the aquatic insects remain largely ignored. If you could use well-described adults in place of undescribed nymphs, many more regions would be able to use aquatic insects as indicators of water quality. I, for one, think that’s a very good thing.

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2011 was terrible year for wildfires in Arizona. We had several mountain ranges burning at once and huge swaths of forest land were reduced to ash. One fire, the Wallow Fire in eastern Arizona’s White Mountains, became the state’s largest fire on record, eventually spilling over into the western part of New Mexico. Homes and cabins burned as firefighters struggled for a month to get the fire under control. It was bad. Really bad.

There are several obvious losses associated with wildfires in forested areas. U.S. National Forests are in place to protect the nation’s timber resources, and a lot of those were burned away in Arizona’s summer fires. People lost homes and businesses and the state lost some fantastic and popular recreational areas. Many animals were displaced during the fires and several species have probably lost breeding grounds and stops along migration corridors. It’s going to a long time before everything’s back to normal in the burn areas and some areas, where the fires razed all the trees, may never fully return to their pre-fire conditions.

Campfires are a common source of wildfires. An improperly tended fire was the likely cause of the Wallow Fire.

By and large, these obvious costs are the things people associate with wildfires, but the damages wrought by fires are much more widespread. Most people don’t even imagine that fires might impact aquatic systems because water doesn”t burn. However, wildfires can destroy aquatic systems and the insects and other aquatic organisms that depend on them.

Fires damage aquatic systems in many ways. Burned trees leave behind massive amounts of ash. Because the Arizona fires occurred before the summer rains began, all that ash was sitting around waiting to be swept into streams and lakes when the rains came. Increased ash in streams usually causes dissolved oxygen to plummet and can cause other changes to the chemical environment of the water such that insects (and fish and aquatic plants and amphibians) die in mass numbers. Even if some things are able to survive in the new water conditions, they might die off anyway if their foods have been eliminated from the system.

The Aspen Fire in the Santa Catalina Mountains, several years ago.

Trees and other vegetation provide stabilization to the soils in forests, holding them in place. When you eliminate the trees, erosion increases dramatically. Soils start to loosen and move about, and rains can get things moving even faster. A lot of this sediment finds its way into streams. Most headwater streams, the sources of streams and rivers, have little sediment and are instead full of large rocks and small boulders. Many insects are adapted to living on or under those rocks and don’t do so well if they’re buried in sand and silt. Sedimentation can therefore eliminate essential habitat for many aquatic invertebrate species. These species will die if conditions do not quickly return to normal. Things rarely return to normal quickly.

Increased erosion leads to another problem: the ability of soils to absorb water decreases dramatically. This means that even gentle rains can sometimes lead to flooding, causing flash flooding in streams. Flash flooding and aquatic insects generally don’t mix (though there are some notable exceptions), and most individuals are swept up in a mass of swirling water full of sand and rocks. These insects are generally ground up into microscopic bits, though a few might be swept out of their habitat and deposited somewhere far downstream. If the habitat conditions in that area aren’t right, they’ll eventually die too.

A little wildfire I came across a few years ago. It quickly burned itself out, thankfully.

The loss of vegetation directly impact the stream as well. Shade is eliminated and water temperatures rise. Insects that depend on cold water might not survive. Vegetation is also a very important food source in the headwater regions of streams, providing essential nutrients to the system as leaves and branches fall into the water. When this food source disappears, so do the insects that depend on it.

Then there’s the problem of fire retarding chemicals that firefighters use to bring wildfires under control. These are important tools for fighting fires, but when it rains, the chemicals are flushed into lakes and streams along with the sediment and ash. If a species is sensitive to this sort of pollution, it’s not going to do so well when it’s suddenly swimming in a toxic stew.

You can see the charred areas where the mesquite trees and agaves burned in the Greaterville Fire in summer 2011. This was one of the little fires.

So, there are lots of ways that fires cause damage to aquatic systems. There’s still one thing to consider with streams though: the water doesn’t stay in one place. You know what that means: the nasty combination of polluted, low-oxygen water, ash, and sediment doesn’t remain within the burn area. Instead, it flows downstream. Rivers many miles from wildfires might thus suffer due to the fire too. Also, the streams in mountain ranges are often headwater streams, the sources of rivers. Damage to the headwaters of a river can have consequences very far downstream and may even cause damage to an entire watershed.

The fires in Arizona may have caused some very long-term or even permanent damage to some streams impacted by the wildfires this year. Some of the fires ravaged areas that are home to rare or endangered aquatic insects. One species of riffle beetle in the Chiricahuas is ONLY found in one stream in that range. If the fires damaged that stream sufficiently to kill the beetles, it will have caused their extinction. Likewise, the White Mountains are home to a protected springsnail that lived right in the middle of the burn area. Will that species, or the very rare caddisfly known from the area, disappear for good? Even the things that aren’t particularly rare might not reappear after the streams recover. If individuals from other populations are too far away to recolonize the damaged streams, some species might never return to burn area streams.

This area, where the protected springsnail is located, probably doesn't look much like this anymore...

I think it will be interesting to see what happens to the streams within the burn areas over the next few years. I intend to collect from the White Mountain streams to see how long it takes for the insects in several streams there to recover from the impacts of the Wallow Fire. By comparing what is found in the stream now and into the future to what I’ve collected in the past, I’ll be able to monitor the stream conditions rather effectively over time. I really hope those streams recover! I doubt they will ever be the same again, but I’d hate it if the actions of people destroy species that we’ve barely even begun to understand.

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A few years ago, my boss was asked to sample some backwaters of the Colorado River in Imperial National Wildlife Refuge. We hauled our sampling gear and boat down to Yuma, AZ and spent half of two very hot summer days (Yuma gets up to 120° in the summer!) collecting water, algae, plankton, and insects. You know what’s hard? This:

Me, sampling insects from the front of a john boat

Collecting on boats is an adventure because the boat moves backwards every time you push the net down into the vegetation, making actually collecting insects (and there were hardly any in this backwater anyway) very difficult. Darn you, physics!

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I promised to post some lesson plans during the semester, but I never had a chance to actually do it. Today I’m making good on that promise. As it’s also related to my recent water quality series, I’ll use this post to finish up the series at the same time!

A few weeks ago, I had the opportunity to teach at a top middle school in Tucson, a school that consistently ranks in the top 10 or 20 schools in the nation. The kids at this school are very smart. I taught 3 lessons, but the kids were in groups of 5th through 7th graders, all mixed together. Odd! These kids were also older than any other kids I’ve worked with over the past semester, so my usual “What is an Insect” presentation just wasn’t going to cut it. Instead, I planned a presentation on aquatic insects.

One part of my presentation involved the kids doing an activity I developed that focused on using aquatic insects as indicators of water quality. For the blog here, I’m going to describe how I ran the lesson in the classroom during the hour I had allotted. However, if anyone wants to use this activity, you can find a more official, printable lesson plan on my Educational Materials page (it will be posted later today – having problems getting it uploaded). Feel free to use and share it at will!

The roaches I share with the kids travel in this

I start all of my insect lessons by figuring out how much the kids already know about the characteristics of insects – number of legs, body segments, antennae, and wings and where their skeleton is located. With the more advanced kids at this school, I also asked about spiders, crustaceans, and other arthropods as well. Once we covered the basics, I got a hissing cockroach out and let them hold and interact with it. The group of kids were mature enough to be able to pass the roach around without totally freaking out and dropping one of my little guys on the floor – one benefit of working with older, gifted kids! We discussed what the roaches eat (they’re decomposers of plants) and how they eat (chewing mouthparts). Then I got a giant water bug out. I don’t let kids hold them so they won’t get bitten, but I showed them all the piercing-sucking mouthpart up close. We compared the mouthparts of the water bug to those of the roach and I had them guess some of the amazing things that giant water bugs are capable of eating.

I had the kids get into four groups and set the tone by telling them that each group was a survey team sampling a different stream in southern Arizona. They’d collected, sorted, and identified the insects in their samples, but they still needed to calculate the biotic index value to determine how polluted the water was in their stream. I gave each sampling team an envelope containing 10 cards, the “insects” in their samples. Each card had a picture, the genus, a common name, and the Arizona tolerance value (see below). Their job was to calculate the biotic index value by taking the average of the tolerance values for all the insects in their sample. I also asked them to count the number of species found in their sample and discuss what the number they calculated said about the water quality in their stream. Then I let them loose!

I let the kids do the math and discuss the results with their groups for about 8 minutes and then got everyone back together. I had one person from each group share the biotic index value for their stream and what they thought that meant. After every group shared their results, I told them which specific streams their “insects” were from (I based my cards on actual samples, so they were accurate!) and a few facts about that stream that might impact the water quality. We discussed their results in light of this new information. For example, everyone decided that it was natural that the most polluted stream would be the one that only had water in it because a waste water treatment plant dumped its effluent into the streambed. It was also natural that the stream that had the fewest human visitors was the least polluted. They also discovered that the number of species was generally higher in less polluted streams than in highly polluted streams and that some insects with very high pollution tolerance values still lived in the cleanest water. Essentially, they came up with all the ideas I had intended to point out, entirely on their own!

The "insects" in the "sample"

The kids were enthralled by the insects that have tolerance values of 11 out of 10, so I ended my presentation by pulling out a water scorpion. They were an example of and 11, and I let everyone get a close look at it. I told them a few facts about the insects and we finished the lesson by briefly discussing why that particular insect might be more tolerant to pollution than other insects. They came up with some great ideas!

All in all, I was happy with the presentation! I think there was a good mix of live insects and fake insects. I did some talking, but the kids spent most of the time making observations and doing the activity. Even though the students at this school might not be the best from which to judge the success of my new activity, the kids seemed to get really into it the activity and asked questions that made it clear that they’d understood the greater implications. I couldn’t have been happier! Although my presentation was rather informal, I have some ideas for how to expand the activity to make it a full-blown science lesson that fits into the national science standards for 5-8 graders. If you’re interested in teaching the activity, check out the lesson plan I’ve posted for more information!

This concludes my series on using aquatic insects as indicators of water quality… for now! I have a few more topics I’d like to cover, but I think I’ll move on to other subjects for a while and revisit this topic again in the future.